The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Rooms containing collections of electrical equipment such as computer servers may be referred to as data centers. Data centers and the equipment contained therein may operate optimally based on air with the appropriate temperature and humidity provided to the indoor environment. Maintaining the optimal environment for a data center often requires providing air at a temperature to remove heat from the data centers.
Devices sometimes known as “air economizers” have been used for space conditioning in conjunction with space conditioning systems that include air conditioning equipment. Space conditioning typically refers to conditioning space in buildings in areas occupied by humans, such as offices. The air economizer introduces outside air into the building to cool the space within the building such as when the temperature of the outside air is lower than the desired temperature in the building.
Electronic equipment in data centers is less tolerant to fluctuations in temperature and humidity than humans. As such, data centers are typically substantially sealed spaces that have vapor barriers where infiltration of air into the data center from outside the data center is minimized. Infiltration refers to air that enters the data center other than through a data center climate control system where it is first conditioned before being introduced into the data center. As such, air economizers are not typically used in conjunction with data center cooling systems. Rather, data centers cooling systems use air conditioned by air conditioning equipment where temperature and humidity are closely controlled to cool the data center. The general approach in data center cooling is to maintain a desired temperature and a desired humidity range while operating within a vapor barrier with less than 5% infiltration. ASHRAE specifies that the relative humidity level for Class 1 and Class 2 data centers be between forty and fifty-five percent.
FIG. 1 shows an example of a typical data center 100 having a climate control system 102. Data center 100 illustratively utilizes the “hot” and “cold” aisle approach where equipment racks 104 are arranged to create hot aisles 106 and cold aisles 108. Data center 100 is also illustratively a raised floor data center having a raised floor 110 above a sub-floor 112. The space between raised floor 110 and sub-floor 112 provides a supply air plenum 114 for conditioned supply air (sometimes referred to as “cold” air) flowing from computer room air conditioners (“CRACs”) 116 of climate control system 102 up through raised floor 112 into data center 100. The conditioned supply air then flows into the fronts of equipment racks 104, through the equipment (not shown) mounted in the equipment racks where it cools the equipment, and the hot air is then exhausted out through the backs of equipment racks 104.
In the example data center 100 shown in FIG. 1, data center 100 has a dropped ceiling 118 where the space between dropped ceiling 118 and ceiling 120 provides a hot air plenum 122 into which the hot air exhausted from equipment racks 104 is drawn and through which the hot air flows back to CRACs 116.
CRACs 116 are coupled to a heat rejection device 124 that provides cooled liquid to CRACs 116. Heat rejection device 124 is a device that transfers heat from the return fluid from CRACs 116 to a cooler medium, such as outside ambient air. Heat rejection device 124 may include air or fluid cooled heat exchangers. Heat rejection device 124 may be a building chilled water system in which case chilled water is the cooled liquid provided to CRACs 116 and CRACs 116 may be chilled water air conditioning systems having chilled water valves. The chilled water valves may be on/off valves or be variable valves, such as capacity modulated valves. Heat rejection device 124 may also be a refrigeration condenser system, in which case a cooled refrigerant is provided to CRACs 116 and CRACs 116 may be phase change refrigerant air conditioning systems having refrigerant compressors. The chilled water valves and compressors of CRACs 116, as applicable, are indicated representatively by dashed box 117 in FIG. 1 and the solid box 117 in FIGS. 2A & 2B.
Each CRAC 116 may include a control module 125 that controls the CRAC 116.
It should be understood that data center 100 can include a plurality of climate control systems 102, each having one or more CRACs 116. In this regard, CRACs 116 shown in FIG. 1 may be part of the same climate control system 102, or may be part of separate climate control systems 102.